The present invention relates to a perpendicular magnetic recording head which, by preventing the occurrence of cross-talk between channels, is capable of increasing the density of tracks.
High density recording has recently been demanded in magnetic recording techniques. For this reason, perpendicular magnetic recording is receiving a great deal of attention as opposed to conventional longitudinal-direction magnetic recording. In a perpendicular magnetic recording system, the magnetic medium is magnetized in a direction perpendicular to its surface, thereby achieving high density recording.
Further, pulse-code modulation (abbreviated hereinafter as PCM) records by converting a voice or picture into a digital code. Since this PCM recording offers a high S/N ratio, and therefore, a recording of high quality, it has been widely used in recent years. In the above-mentioned recordings of high density and of high quality, if the track of a recording medium is multichannelled and simultaneous recording is effected with respect to each channel, it will possible to effect a recording of higher density as well as of higher quality.
A prior art perpendicular magnetic recording head is arranged such that, as shown in FIG. 1, a main magnetic pole member 12 and an auxiliary magnetic pole member 14 are disposed with a magnetic tape 10, constituting a recording medium, interposed therebetween. The main magnetic pole member 12 has a thin film formed of magnetic material of high permeability and its tip end portion slidably contacts a recording surface of the magnetic tape 10. The auxiliary magnetic pole member 14 is formed of magnetic material of high permeability and is wound with an exciting coil 16. When a signal current is applied to the exciting coil 16, a magnetic field corresponding to the signal current is generated from the auxiliary magnetic pole member 14 to be foucused onto the tip end portion of the main magnetic pole member 12. Due to this magnetic field, a residual magnetization is produced in a direction perpendicular to the magnetic tape 10, and the signal is thus recorded on the tape 10.
On the other hand, a ring-type magnetic head for used in longitudinal-direction magnetic recording is constructed such that, as shown in FIG. 2, magnetic cores 18 and 20 oppose each other in such a manner as to assume the shape of a pair of opposing capital letters C's, and gap 22 is created between the opposed face of one side. When a signal current is allowed to pass through an exciting coil 24 wound around the cores 18 and 20, a closed magnetic circuit is formed within each of the cores 18 and 20. As a result, a residual magnetization is produced, due to the action of a magnetic flux leaked from the gap 22, in a direction perpendicular of the surface of the magnetic tape 10, whereby the signal is recorded thereon.
In this ring type magnetic head, since the magnetic flux is not leaked except in the area of the gap 22, multichannelling would not cause the crosstalk between the channels to have any substantial effect upon the recording characteristics. However, since the perpendicular magnetic recording head has an open magnetic circuit formed between the main magnetic pole member 12 and the auxiliary magnetic pole member 14, the following drawback occurs when, as shown in FIG. 3, a number of magnetic heads are juxtaposed with each other for multichannelling arrangement. That is, the magnetic flux generated from one main magnetic pole member 12 or one auxiliary magnetic pole member 14 enters the adjacent main magnetic pole member or auxiliary magnetic pole member, as indicated in FIG. 3 by broken lines. This entry of the magnetic flux causes the occurrence of crosstalk between the channels, thereby deteriorating the recording characteristic of each head. In the prior art perpendicular magnetic recording head it therebecomes difficult to effect multichannelling .
Further, the width of the main magnetic pole member 12 is substantially equal to the width T of a track. On the other hand, the width W of the auxiliary magnetic pole member 14 is preferably several times greater than the width T of a track. Further, it is necessary to provide an interspace between the auxiliary magnetic pole members 14 which is large enough to permit the exciting coil 16 to be wound therearound. For this reason, it is impossible to make the pitch P between the tracks small owing to restraints upon the shape and structure of the auxiliary magnetic pole member 14, resulting in a drawback that the prior art perpendicular magnetic recording head fails to increase the density of the track.